small wireless device project

Discussion in 'The Projects Forum' started by Macabra, Jun 8, 2009.

  1. Macabra

    Thread Starter Active Member

    May 31, 2008
    Hi everyone,

    I'm interested to make a device in which with a push of a bottom, it sends a signal wirelessly to a main unit located in the same room where it then performs bunch of other stuff. My question is, what is there available for me that could be cheap and that I can use. I want this to be small (something like that could be worn around neck or something or on wrist (etc).

    I know of Xbee, but my experience with those is that there is this rather big wireless module to communicate between the microcontrollers. I also know of bluetooth, but I don't know if there's such a thing that is that small.

    Anyone know?

  2. balisong


    Feb 26, 2008
    Does it have to be invisible and/or silent?
    I've modified a keychain LED flashlight into an IR transmitter.
    The receiver recognizes single/double & long/short pulses for four different functions.
    The parts were less than $10 plus the sacrificial flashlight.
  3. radiohead

    Distinguished Member

    May 28, 2009
  4. John Luciani

    AAC Fanatic!

    Apr 3, 2007
    XBees have an internal microcontroller. You wire the button directly to the XBee and
    have it transmit when the button changes state. It is big but bluetooth modules are
    big too.

    (* jcl *)
  5. Propaganda


    Jun 3, 2009
    xbee/BT is large and might be WAY overkill for the project depending... how much bandwidth do you need? Mission critical? Do you need ACK?

    Look into a simple 4800bps RF pair... they also sell a demo kit with xmitters the size of automobile keyless entry keychain units.

    If you needed serious bandwidth, say 2,000,000bps you can get a SPI controlled nRF24L01, "Decibit" sells the chip on a premade board, they are several gold stars! (i used these babies.
  6. Macabra

    Thread Starter Active Member

    May 31, 2008
    Thanks for the suggestions, I was actually looking into something like keychain deal like one of the members posted. Yeah, a BT/xbee would be overkill. Nope, I do not need's pretty much Simplex..just press a button and somehere in the house the system just does what I want it to do.
  7. Steve C

    Active Member

    Nov 29, 2008
    if you want a designed solution, find car alarms and keyless entries on ebay, then sort by price to find the absolute cheapest you can find. All you'd be looking for is a 1 channel remote. They should all work. Just add a wall wart and you are good to go.

    If you intend to carry the remote around on your person, check out autopage. The remotes are 8 channel, letting you control any number of devices (uh, up to 8). I use 4 channels to control my car alarm, 2 channels to control my wife's car, one channel to control my garage door, and that still leaves me with an open channel I could use to duplicate what you are looking to do. More expensive than the cheapest stuff ebay has to offer, but it's something to think about, especially if you intend to carry or wear it. I demand I carry as little as possible, and an extra remote is a no-no.

    Also check out k-9 sombra. More expensive also, but it contains an rfid proximity sensor which would automatically "press the button" simply when you walk into the room/house, eliminating the need to push anything. Unless that isn't the intended app. But still neat to think about.
    Last edited: Jun 11, 2009